The present invention concerns a pipeline for transporting a medium, in particular a liquid with abrasive solid particle contents, for example, sludge, comprising a lining comprising plastic material for protecting an inner side of the pipeline, wherein the pipeline comprises pipes welded together that are provided on their inner side with at least one lining section arranged at a spacing from the weld seam. Moreover, the invention concerns a method for producing a pipe with a lining that is suitable for transporting in particular liquids having an abrasive solid particle contents wherein for constructing the pipeline individual pipes are butt welded together and the pipes are provided with lining sections comprising a plastic material, wherein the lining sections are spaced from a pipe end.
Abrasive liquid/solid mixtures are transported often in a pipeline or conduit that is provided with a lining, i.e., an inner protective coating. This protection serves, on the one hand, for mechanical loading of the, particularly, metallic inner side of the pipeline wall as well as for preventing corrosion of the pipeline wall. As an alternative, and/or as a supplement, the lining serves the lining can also serve as a protection of a corrosion coating that may be applied onto the metallic inner side of the pipeline.
When welding the pipeline from individual pipes heat is produced that will propagate toward the pipe member. A lining that is comprised of plastic material or a lining section of a pipe however may be loaded only up to a certain temperature with thermal energy. This depends on the coating material and the application method. When the temperatures are too high, the coating material can be negatively affected with respect to its properties up to the point of reduced adhesion of the lining on the inner side of the pipe, preferably consisting of steel, or of complete destruction of the lining. It is therefore known to not extend the lining to the end of the pipe but to leave a so-called “cutback”. This area, after welding of the pipes has taken place, must be post-coated. The post-coating is especially difficult in case of thicker wear-resistant plastic linings with a thickness of, for example, 20 mm to 50 mm in the radial direction.
The post-coating of the area that has been spared is enabled by introducing a sleeve into the interior of the pipeline that extends from one lining section to the next, and by filling the space that is now closed off. Subsequently, the sleeve is left within the pipeline which negatively affects the inner pipeline cross-section. Because of connecting locations relative to the weld seam positioned at both ends of the sleeve and in need of sealing, these pipelines often have leaks that may extend to the weld seam and that, already at the beginning of pipeline operations, may have a negative effect on the integrity of the pipeline as a result of the transported media.
It is therefore an object of the present invention to provide a pipeline and a method for producing a pipeline that is improved relative to the prior art.
The object is solved in regard to the pipeline in that at least one lining section of a first pipe rests on a lining section of a further pipe by forming an undercut such that in the circumferential direction of the pipeline a fill space is formed as well as by a method characterized in that, upon alignment of the pipes for welding, lining sections of the pipes rests against one another, wherein by an undercut at least one lining section forms a fill space that after welding is filled with a fill material that in situ will cure and/or will be cured. Advantageous embodiments of the invention can be taken from the dependent claims as well as from the description.
A pipeline according to the invention for transporting a medium, in particular a liquid with abrasive solid particle contents has at least one lining section of a first pipe that rests on a lining section of a further pipe by forming an undercut such that in the circumferential direction of the pipe or the pipeline a fill space is formed.
In a method according to the invention for producing a pipeline with a lining, preferably a pipeline as disclosed above or as described in the following, individual pipes are butt welded together for constructing the pipeline, wherein the pipes each are provided with at least one lining section comprising plastic material which lining section is spaced from the pipe end. Upon alignment of the pipes for welding a lining section is designed such that by means of an undercut a fill space is formed which, after welding, is filled with a filler material that in situ will cure and/or will be cured. Pipes that abut end on end have in general identical longitudinal center axes, independent of the abutting edges of the pipe walls that, for example, as a result of beveling, may extend at a slant to one another.
The lining sections of two neighboring pipes are therefore directly abutting one another so that a fill space is produced that at least section-wise, in particular however completely, is separated relative to a free pipeline interior, i.e., is inwardly closed. Into this fill space, by omitting sleeves to be introduced into the interior of the pipeline, a filler material can be introduced. Producing a pipeline for transporting abrasive mixtures is thus simplified. At the same time, it can be ensured that the abrasion-resistant lining sections continue in constant quality across the length of the pipeline. Complex pipe couplings with which the same result can be achieved are not needed.
As a lining or thicker coating of an inner side of a pipeline preferably an organic polymer, in particular polyurethane, is to be used that with regard to properties can be matched to the media to be transported. For example, between the inner side of the pipeline and the coating, a corrosion protection layer and/or an adhesion promoter or an adhesive that improves the connection of actual lining and the inner side of the pipeline to be protected may be applied. The inner side of the pipeline is constituted in this way, for example, of the metallic or additionally coated inner sides of the pipe walls of the individual pipes. In particular after filling in the fill space with a material that is identical to the material of the lining section a continuous identical lining of the pipeline is provided. The properties of the sealing and/or abrasion-inhibiting material are continuously assessable.
Inasmuch as the fill space of the pipeline is to be filled, an undercut is advantageous that has a profile that is suitable for producing a positive-locking connection. Even in case of undesirable detachment of the lining from an inner side of the pipe wall, caused by unsatisfactory adhesion, at least in the longitudinal direction of the pipeline forces that are produced in the lining can be better transmitted by a lining section even across the fill space.
A pipeline according to the invention is furthermore improved when the two lining sections abutting one another have sections that overlap one another, viewed in the longitudinal direction of the pipe. Overlap existing in the radial direction of the inner linings resting on one another increases the contact surface which, in turn, leads to a greater seal-tightness of the fill space relative to the interior of the pipeline.
Preferably, the inner pipeline cross-section at the transition from one pipe to a further pipe connected by welding is substantially constant. Substantially constant means in this context that the inner pipeline section has no deviations that surpass the conventional manufacture-caused tolerances. The pipeline cross-section is not reduced by sleeves that are permanently installed in the pipeline.
Advantageously, the weld seam of a pipeline is limited at the inner side of the pipeline by a root protection that in particular may be integrated into a support ring or a sleeve that then also serves for centering the pipes relative to one another. A root weld protection serves moreover for protecting the lining from weld spatter and provides a flawless root weld.
Advantageously, the fill space after welding is filled in, in particular, the fill space is filled by means of at least one opening provided in a wall of the pipeline, in particular of a pipe, so that no complex devices must be introduced into the pipeline. The openings after filling are to be closed and secured.
The undercut of at least one lining section is advantageously formed by use of a correspondingly embodied cap during centrifugal casting of the pipe for producing the lining section. The use of identical undercuts that adjoin one another at least at the contacting faces of the two pipes reduces the manufacturing expenditure and the possibility of positioning two pipes that have lining sections that, with respect to their profiles, do not match one another, which in situ would lead to significant delays. Advantageous is at least one pipeline in which the fill space is formed by undercuts of both participating lining sections.
The connecting location between two pipes is further improved when an adhesion promoter is applied to the undercut between the fill space and the lining section.
The manufacturing method according to the invention is further improved when the fill space and/or at least one lining section is tempered preferably by induction after the welding step. Alternatively, or in addition to tempering by induction, resistance heating elements or infrared radiators can be employed, for example. A thermal after treatment can lead to a faster curing of the material introduced into the fill space.
Optionally, a support means that is preferably temporarily inserted into the pipeline may improve the formation of a continuous lining of the pipeline when this support means is arranged in the pipeline during welding and/or during filling and/or during a solidification process of the filler material. As a support means, a support ring can be used for a root weld seam, for example; otherwise also a support member, for example, an expander or a balloon. These means may also contain heating elements with which a curing process can be accelerated.
An additional heat dissipation can be realized during welding by means of a heat dissipating means, for example, a copper material, that is applied externally onto the pipeline. Moreover, purging with an inert gas can be realized during welding in particular by means of one or several openings introduced into the pipeline.